1. Technical Field
The present invention relates to a micro-dialysis probe having a supply line and a drainage line for a drip-feed solution and a dialysis section positioned generally therebetween. More specifically, the present invention relates to a micro-dialysis probe wherein solution flowing from the supply line to the drainage line experiences an inversion in flow in the area of the dialysis section.
2. Description of the Related Art
Implanted hollow fibers, hollow fiber loops or dialysis probes are used for micro-dialysis in medicine and biological research. Conventional dialysis probes possess a tube-shaped shaft in which dialysate is drained and which comprises a closed cylindrical membrane (hollow fiber sealed on one side) into whose interior a thin tube protrudes, for supplying the drip-feed solution. Between the drip-feed solution flowing back and the ambient medium, dialysis at the hollow fiber membrane leads to a concentration equalisation in the permeable substances. Probes with the same principle design are also known, in which the dialysis fiber is surrounded by a non-buckling casing or framework which it partially protrudes out from, said dialysis fiber being supported by said casing or framework. Such a dialysis probe is known, for example, from DE 33 42 170 C2.
In the use of viscous drip-feed solutions or at high flow rates in particular, it is evident that the flow through such dialysis probes is not optimal. Lateral pressure upon the probe can move the inner tube slightly out of its central position and the flow profiles via the hollow cylinder are changed. The flow can slow up or come to a standstill on the side where the gap between the outer and inner cylinder is very narrow, while a fast-flowing preferential path forms on the opposite side. Moreover, a dead space arises in the shaft in which the dialysate is drained, due to its construction, at the transfer point into the drainage tube. Both of these lead to a delay in the adjusting of the equilibrium.
To stabilise the position of the inner tube in the hollow fiber, DE 197 14 087 A1 has proposed, for such probes, surrounding the capillary with a profile. Profiles with such a small diameter and a central bore, however, can only be produced at great cost.